368 PATHOGENIC BACTERIA. 



discrete, irregularly rounded, opaque masses of a yellow- 

 ish-white color. The surfaces of the colonies are tuber- 

 ciliated, and an appearance somewhat like a lichen is 

 observed (see Fig. 78). 



Upon potato very dry scales of a pale-yellow color 

 rapidly develop. 



The growth upon blood-serum is less luxuriant, but 

 similar to that upon agar-agar. 



In milk the organism produces no coagulation by its 

 growth, and does not alter the reaction. 



Microscopic study always reveals the organism as the 

 same tangled mass of filaments seen in the tissues. The 

 old cultures are rich in spores, which are very small and 



Fig. 78. — Streptothrix of farcin du bceuf growing on glycerin agar-agar. 



develop upon the most superficial portions of the growth. 

 These spores resist the penetration of stains to a rather 

 unusual extent. 



Cultures retain their virulence for a long time : Nocard 

 found one virulent after it had been kept for four months 

 in an incubating oven at 40 C. 



